If multiple creatures block a creature with trample, the attacking player assigns damage to the blocking creatures equal to the power of the attacking creature. Ex. A creature with power 10 and trample attacks. You block with 4 creatures. The attacking player may assign the 10 damage as he/she chooses among the blocking creatures. If any damage is still left over, that would go through to you, the defending player. Note: The attacking creature will take damage equal to the combined power of all blocking creatures.
Creatures with Flying may block creatures that don't. Note that in Magic, creatures do not 'attack directly' as such, they are declared as attackers, and then creatures may be declared to block them. The creature with Flying in this case, can block creatures with, and without Flying.
If creature has Reach, it can block flying creatures without having to have flying itself.
If a creature has Intimidate, when it attacks, it can only be blocked by creatures that share a colour with it, or artifact creatures.
Island-walk A Land-Walk ability(Example:Swamp-walk, Mountain-walk) If opponent controls an island this creature is unblockable. Creatures with land-walk abilities can not block each other.
Since you don't attack creatures in Magic (you declare attacks, and the opponent may choose to block if he wants) then it's almost a moot point. Technically a Planeswalker could become tapped and be attacked, however the outcome is no different. Nor is there any difference if a creature declares a block, and then becomes tapped.
Trample means you runn over other players defence and hits players life
Defending creatures deal damage to an attacking creature's toughness when they block equal to their power. It's called 'blocking', not 'attacking back'. Summoning sickness has no affect on blocking. Summoning sickness is the inability of a creature to use tap (tap symbol) abilities or attack until the next turn of the owner who summoned it.
'Trample' allows a creature to deal damage to a player even it is blocked. When damage is dealt, it needs only assign 'lethal' damage to the blockers, the rest is dealt to the player. 'Lethal damage' is considered to be damage equal to the blocker's toughness, it does not take 'Protection' or 'Indestructable' into account. So take a situation where an 8/8 trampler is blocked by a 1/1 creature with indestructable, and a 1/1 creature who has protection from the colour of the attacker. The attacker can deal 1 damage to each, and the remaining 6 to the opponent, it doesn't matter that both creatures survive the 'lethal' damage. As a last note, a creature with both Trample and Deathtouch needs only deal a single point of damage to any blocker, regardless of toughness. So if that same creature above was blocked by two 3/3 creatures, it still can deal just one to each and the rest to the player. Without Deathtouch it would be forced to deal 3 to each, and only 2 to the player.
'Artifact' is a card type, not a creature type. You can't pick 'Artifact' for the purposes of Extinction. Most artifact creatures have a creature type too - construct, myr, etc, but if it doesn't, then it is technically immune to Extinction, like Morphs.
Eldrazi monument gives all your creatures flying, indestructible and +1/+1, but it requires that you sacrifice a creature every upkeep
No, they are not impervious to all magic. There are a few myths and legends about dragons that were captured or slain, usually because of dark magic. For the most part, dragons are amazing creatures, but even an amazing creature can be defeated now and then.
Yes of course - it says 'each creature', so your creatures take the damage also. If a card only affects the other players' creatures, then it will say so on the card.